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Temperature-dependent decline in the external quantum efficiency (EQE) of blue light-emitting diodes, which is at a maximum at j 40 A/cm2 the decline in the external quantum efficiency in the continuous-wave and pulsed modes is determined by the loss in nonequilibrium filling by delocalized carriers of states associated with the lateral inhomogeneities in the composition of the solid solution outside the space-charge region, as well as by the loss due to the interaction of delocalized carriers with extended defects.

The obtained experimental results allow us to clarify the nature of mechanisms related to the presence of cations in disordered InGaN alloy and hetero-interfaces. The capture of charge carriers by cations reduces the external quantum efficiency (EQE) in green MQWs at j < 10 A/cm2. The EQE droop phenomenon caused by smoothed out lateral potential fluctuations occurs at j > 10 A/cm2. At j > 40 A/cm2 the droop associated with interactions between charge carriers and dislocations and grain boundaries takes place.

LEDs operating under high pulsed current density, which excludes self-heating, are of great interest for different applications, in particular, for pumping lasers with a short time of activator relaxation, such as Ti:Sapphire. The current dependences of the efficiency emission spectra as well as the rise and fall times of high-power blue and green LEDs were investigated under extremely high pulse current density up to 7 kA/cm2 and a pulse duration of 100 ns to 3 μs. An analysis of the pulse behaviour of the LEDs reveals that the main droop in efficiency and a change in the spectrum occur up to the current densities ∼ 1 kA/cm2 and seem to be non-thermal. The energy and spectral pulse characteristics of the radiation were studied with simultaneous recording the excited Ti:Sapphire photoluminescence in order to determine the optimal pumping conditions.

The contribution of several mechanisms to the external quantum efficiency (EQE) droop in blue InGaN/GaN LEDs occur at different current densities j and voltages in MQWs situated inside and outside of a depletion region around p-n junction. It is clarified that an increase in EQE droop at 300-400 K (j < 10 A/cm2) is due to non-radiative losses related to an enhancement in trap-assisted tunneling. It is also associated with a growth in the concentration of delocalized carriers. The main source of the EQE droop under direct current and at pulse mode when j > 30 A/cm2 is non-equilibrium filling of lateral regions of different size within MQWs placed outside of depletion region by delocalized carriers activated by injection when voltage exceed a threshold value (U > Uth). This leads to a decrease in localized potential and to the blue shift of EQE maximum over wavelengths followed by the EQE droop.

It is shown that a three-dimensional fractal–percolation system is formed in nanomaterials of light-emitting InGaN/GaN and AlGaN/GaN structures in the presence of conducting extended defects and local inhomogeneities of the composition of the solid solutions; this system determines the electrophysical properties of light-emitting diodes fabricated on the basis of these structures. The geometry and properties of this system depend nonlinearly on the degree of disorder in the nanomaterial of the structures, on the value of the injection current, and on the rate of alloy growth.

One of the interesting materials for the antireflective coatings of photovoltaic converters based on InP is the anodic oxide of indium phosphide. This material might be used as a first layer of a multilayer antireflection coating, as well as an independent single-layer antireflection coating. This paper deals with the study of the coating and research of its effect on the reflection coefficient from the InP surface.

The results of the degradation study of commercial InGaN/GaN LEDs with the external quantum efficiency (EQE) ∼ 40–50 % at 450–460 nm are presented. It has been clarified that one of the mechanisms responsible for EQE degradation and the unpredictable failure of LEDs is the multiphonon recombination of carriers. The distorted forward branch of I-V characteristics at U < 2V and the appearance of the SI ∼j4 section on the current spectral noise density dependences on current density in LEDs before or after 100 hours of aging test are the criteria identifying an unpredictable failure.

Low-frequency noise measurements, combined with the conventional techniques for the study of InGaN/GaN-based LEDs, make it possible to separate the contribution of conductive paths associated with the extended defect system (EDS) and point defects (PD) to non-radiative recombination processes. These measurements also can reveal physical mechanisms leading to the unpredictable failure of LEDs, such as non-uniform current distribution, local overheating, and presence of local InGaN regions with a reduced band gap width E g .

It was shown that the contribution of 3D nanoscale indium fluctuations into the efficiency droop at j 50 A/cm2 and the current dependences of efficiency, approximated by as η (j) α j-b where 0.2 < b < 0.3, are alike in both green and blue LEDs.